1. Field of the Invention
The present disclosure relates to an inkjet printing apparatus and a method for controlling an inkjet printing apparatus.
2. Description of the Related Art
Inkjet printing apparatuses are widely used in the field of printing images, such as monochrome and full-color images. In a printing head of an inkjet printing apparatus, when a nozzle that discharges ink from the printing head is exposed to the atmosphere for a long time, a discharging failure caused by, for example, the adhesion of dust or the drying of ink near the discharge nozzle tends to occur. In order to prevent such a discharging failure, a preliminary discharging operation method (hereunder may simply be referred to as “preliminary discharge”) for preliminarily discharging ink that does not directly contribute to a printing operation is proposed. In other words, in order to guarantee a time in which normal discharge from the printing head is expected (hereunder referred to as “printable time”), a preliminary discharging operation is performed by discharging a predetermined amount of ink to a discharge port surface of the printing head at a predetermined time interval.
For example, US 2004-0041873 (Patent Literature 1 (PTL 1)) proposes a method for performing a preliminary discharging operation with respect to a discharge nozzle in accordance with the number of discharges of ink that is discharged from the nozzle (that is, the discharge amount of ink from the nozzle). More specifically, the preliminary discharge is performed when the number of discharges of ink from the discharge nozzle is less than a predetermined number of discharges of ink from the discharge nozzle within a predetermined time, whereas preliminary discharge is not performed when this value is greater than or equal to the predetermined number of discharges of ink from the discharge nozzle within the predetermined time.
In PTL 1, although preliminary discharge control is performed in accordance with the number of discharges of ink discharged for a printing operation, it cannot be said that the reduction of consumption of ink that is used in the preliminary discharge has been sufficiently considered. Therefore, there is room to further reduce the consumption of ink that is used in the preliminary discharge.
For example, in forming an image on a printing medium using ink that is discharged from a plurality of nozzles, a surrounding ambient humidity may increase as a result of evaporation of moisture in the ink from an area where an image is formed. However, in the state of the art including the invention of PTL 1, consideration has not been made while focusing on the application of a humidification effect resulting from the evaporation of the moisture in the ink that is included in the image in this area when a front surface of the nozzle (discharge port surface) passes above the area where the image is formed.